Scanning tunneling microscopy of Ni deposited on Au(l 11) at room temperature reveals strikingly ordered island nucleation. Ni islands grow with spacing 73 A along [121] in rows 140 A apart at surfacelattice dislocations induced by the Au(lll) "herringbone'* reconstruction. The island arrays are explained by a model in which Ni atoms diffuse on the surface and aggregate at these dislocations. Island size varies by more than the shot-noise limit, suggesting that the initial sticking probability is low when a diffusing atom encounters a dislocation.

The scanning tunneling microscope reveals that Ni deposited on Au(111) at room temperature forms regular arrays of two-dimensional islands. The islands grow with spacing 73 Å in rows 140 Å apart at sites determined by the Au(111) ‘‘herringbone’’ reconstruction. This nucleation at evenly spaced sites yields islands with a narrow size distribution. The apparent Ni island height (1.9 Å) is bias-independent and agrees with a hard-sphere model of pseudomorphic Ni/Au(111). The behavior of Ni is contrasted with Au deposited on Au(111), for which far fewer islands are formed.

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